Device Global Discovery

 

Device Global Discovery

Overview

The “Device Global Discovery” diagnostic fails when excessive amount of Global Who-Is requests are observed. A Global Who-Is request may flood the OT network with I-Am broadcast messages, because it requires every BACnet device to respond with an I-Am message. Too much broadcasting within an OT network can lead to denial-of-service (DOS), performance degradation, instability, and other disruptions.

Causes:

• Configuration Errors: One or more BACnet devices have been (mis)configured to issue an excessive number of Global Who-Is requests.

• Device Instability: If devices are frequently rebooting or experiencing connectivity issues, they might initiate repeated discovery requests upon reconnection.
• Device or Network Scanning: Unauthorized scanning or probing of the network can lead to an increased number of discovery requests.

Implications:

• Device Overload: High numbers of discovery requests could be a sign that devices are overwhelmed, resulting in inconsistent responses and further requests.
  
• Broadcast Storms: A broadcast storm, which occurs when devices flood the network with broadcast messages, can lead to a spike in discovery requests.
  
• Network Performance Degradation: High levels of discovery requests can saturate the network bandwidth, causing performance degradation for other network traffic.

How to fix it

• Review and adjust device discovery configuration settings.
  
• Investigate device stability and connectivity to prevent unnecessary reboots and communication issues.
• Device vendors may have newer software/firmware with improved device discovery methods